sortmc
==============================================

Purpose
----------------

Sorts a matrix on multiple columns.

Format
----------------
.. function:: y = sortmc(x, v)

    :param x: data to be sorted
    :type x: NxK matrix

    :param v: contains integers specifying the columns in order, that are to be sorted.
        If an element is negative, that column will be interpreted as character data.
    :type v: Lx1 vector

    :return y: sorted matrix

    :rtype y: NxK matrix

Examples
----------------

:func:`sortmc` keeps all rows together. After it sorts on the first specified column,
it will continue to sort the rows of the matrix using the other specified columns ONLY
when there is a tie in the first column. For example:

::

    x = { 9 2 5 6,
          3 6 1 9,
          3 7 4 1,
          1 2 8 9 };

    s1 = sortc(x, 1);

    sm = sortmc(x, 1|2);

will return:

::

         1      2      8      9
    s1 = 3      7      4      1
         3      6      1      9
         9      2      5      6

         1      2      8      9
    sm = 3      6      1      9
         3      7      4      1
         9      2      5      6

In the output above, we see that the difference between *s1* and *sm* is
that the second and third rows have been switched. This is because :func:`sortmc`
first sorted the matrix based upon row one like :func:`sortc`. Then :func:`sortmc` sorted the
rows in which the first column was the same (in our example they are both threes),
based upon the values in the second column.

Source
------

sortmc.src

.. seealso:: Functions :func:`sortd`, :func:`sortc`, :func:`sortcc`, :func:`sorthc`, :func:`sorthcc`